The present invention relates to a musical tone synthesis apparatus having a processor to synthesize a musical tone.
The conventional musical tone synthesis apparatus is comprised of an input unit for inputting performance information, a tone generator unit for generating a waveform of a musical tone, and a central processing unit (CPU) for controlling the tone generator unit according to the inputted performance information. The CPU operates according to the inputted performance information to execute performance process such as channel assignment and parameter conversion for driving the tone generator unit. The CPU feeds parameters and note-on commands to assigned channels. The tone generator unit is composed of an internal tone generator for generating a wave-form of a musical tone based on the fed parameters, or an external tone generator receptive of MIDI data. In another case, the musical tone synthesis apparatus is comprised of a general purpose computer such as a personal computer which utilizes a software module of a tone generator to synthesize a waveform of a musical tone by processing input performance information such as MIDI event data. The program is installed in the computer to carry out the tone generation processing without use of a hardware module specialized for the tone synthesis. The computer can generate the musical tones by means of the software module or program, the CPU for running the program, and a D/A converter chip for converting the synthesized waveform into a corresponding audio signal.
The conventional musical tone synthesis apparatus composed of the personal computer executes application programs such as a tone synthesis program for synthesizing waveforms and a sequencer program for automatic play of music. However, the computer may incidentally suffers from stop or hangup of the application program so that the program no longer be executed. If the program is hung up in the middle of outputting a note-on or key-on command, a corresponding musical tone may be sustained to sound abnormally. Further, when the application program is accidentally stopped or hung up, supply of waveform data of a musical tone to the D/A converter may be turned off by interruption. Consequently, the D/A converter outputs a direct current which might cause a subsequent sound system to generate click noise. Even worse, leakage of the direct current might damage a loudspeaker contained in the sound system.